This may seem obvious, but the most important command you can teach a dog is "No".
Dogs love training, bond with the dog and it'll spend the rest of its life trying to figure out how to please.
Choose commands carefully, and don't change them. Commands should be given the same way every time.
Silent commands are best actually, but that comes later. using consistent hand and eye signals along with your verbal commands makes it a lot easier down the road.
If you can get the dog to take silent commands, and obey a command to be silent, you've done well, and you'll have a dog that's actually helpful in a lot of situations.
"stay" is usually the toughest one to get right, they'll stay for a while, or as long as you're within sight, that's easy, tough is getting them to stay until released. My dobie didn't figure that one out until she failed to comply with "stay in the truck" and got left at a friends for a few hours...
She'll sit in the back of my truck all day if I tell her to, no matter the temptation, some of that is just her nature though, mostly it's training.
Time is the thing really, it's a lot harder if you're gone all the time. If the dog is with you most of the time for the first six months that's 90% of it if you're consistent.